1. Field of the Invention
This invention relates to a force sensitive handle for a hand operated implement. More particularly, it relates to a force sensitive handle which produces a warning signal upon detection of a force above a desired level. Most particularly, the present invention finds use in a toothbrush handle to sense the applied brushing force and produce a warning indication at a predetermined force level.
2. Description of the Prior Art
Effective toothbrushing requires a user to impart a controlled amount of force in applying the toothbrush to the teeth. If too little force is applied, ineffective cleaning results. If excessive force is used, injury to the surface of the gums surrounding the teeth, as well as excessive erosion of the enamel, dentin and root on the teeth, can result. It has been found that a brushing force, applied normal to the teeth, of 200 to 300 grams is required for effective brushing.
Various devices have been designed to teach the proper brushing force to be imparted during toothbrushing in order to obtain effective cleaning without damage. U.S. Pat. No. 4,253,212 discloses a pressure detection device which may be provided inside or outside of the stem of the toothbrush.
U.S. Pat. Nos. 4,476,604 and 4,680,825 disclose toothbrush holders which sense the amount of force being applied to the toothbrush. Each holder clamps onto and about the toothbrush handle and emits an audio or visual signal when a certain force is applied. The holder is adjustable to permit the users to change their brushing habits by incrementally increasing the applied force until the desired level is reached.
The devices disclosed in these prior patents have several drawbacks. The devices disclosed in the '212 patent require a separate training appliance which is attached to a toothbrush handle. This separate add-on training appliance extends the handle to a longer than standard length. This affects the balance of the toothbrush and the user's grip, which can cause variations in brushing force once the training device is removed. Thus, it produces an unnatural instrument.
The pressure sensing toothbrush holders disclosed in the '604 and '825 patents are also add-on devices which attach to the toothbrush handles. Additionally, the holders are bulky in comparison to the toothbrush handle itself and require the user to adjust their grip to accommodate the larger holder size. Once again, they produce an unnatural instrument.